DF is a grab bag of players of various skills, experience and attitudes. You never know what you're going to get. With PF, you have a bit more control over who joins... Sorta... In theory anyway.

You can still use PF to form your own learning group for old content, though it is still possible that you'll get that one person (or persons) who just want to one-shot everything and they get their knickers in a twist when it doesn't happen in a learning party.